1. Field of the Invention
The present invention relates to a method for renovation of underground pipelines preferably for sewage, comprising introduction of a lining pipe into an existing pipeline, said lining pipe having a length corresponding to the length to be renovated, and consisting of a fusable polymer in a folded condition, and unfolding of the lining pipe in order to line the pipeline.
2. Description of the Invention Background
Folded pipes have already been used for lining pipelines for example according to SE-911948-9, where above all a combination of PE and PVC has given the prerequisites of the use of the concept relating to folded pipes. The basic concept of this technique is that a length of coiled prefabricated folded pipe material without transverse welding is transported successively into e.g. a manhole and is located in an existing pipeline to be lined, said pipeline connecting to the manhole. Introduction of a pipe in a folded condition makes possible to line with a pipe having the same outside diameter as the inside diameter of the existing pipelines. Thereby the capacity of the pipeline substantially can be maintained, no additional arrangements for fixing the pipe in its longitudinal direction being required and the connection of so called service pipelines being facilitated. When lining larger pipelines (.O slashed..gtoreq.300 mm) this technique has, however, not been possible to use, mainly due to difficulties in handling folded pipes of souch dimensions. This as a consequence of larger handling forces being required as well as problems with cracking in the fold areas of the pipes of larger dimensions. Moreover, the coils of the folded pipes have also been difficult, if not impossible, to handle in a normal environment, not the least of which is transportation on a truck, as a consequence of the dimensions of the folded pipes. This means, generally speaking, that the diameter of such a coil be in order not to require special transport, must not be larger than 2400 mm. In order to unfold lining pipes according to conventional methods it has also been necessary to preheat the lining pipe to a temperature of between 100.degree. C. and 120.degree. C. Moreover, at the lower temperature it has been necessary to apply an inner over-atmospheric pressure of about 5 bar, which for large dimensions sets high demands on security arrangements around the lining operation.